1. Field of the Invention
The present invention relates to a data storage disk drive having an optical head, a magnetic head, or a magneto-optic head for reproducing data from and/or recording data on a data storage disk such as a compact disk (CD), a video disk (VD), a magneto-optic disk, a magnetic hard disk, or the like.
2. Description of the Prior Art
Some data storage disk drives have optical heads, such as optical pickups, for reproducing data from and/or recording data on CDs, VDs, magneto-optic disks, or the like. Such a data storage disk drive includes an actuator for moving the objective lens of an optical pickup toward and away from a disk surface along its optical axis normal to the disk surface, and a detector for detecting changes in the distance between the objective lens and the disk surface due to disk surface fluctuations, based on the astigmatic principles or the like. To prevent a laser beam applied to the disk surface by the optical pickup from being out of focus on the disk surface, the actuator is controlled based on a focusing servo signal from the detector to move the objective lens for keeping the objective lens spaced a constant distance from the disk surface at all times regardless of disk surface fluctuations.
FIG. 1 of the accompanying drawings shows a conventional data storage disk drive having a magneto-optic head assembly capable of reading data from and writing data on a magneto-optic disk 1.
As shown in FIG. 1, the magneto-optic head assembly includes an optical head 31 for applying a laser beam to the magneto-optic disk 1, the optical head 31 being positioned on one side of the magneto-optic disk 1, and a magnetic head 32 for generating and applying a DC magnetic field to the region of the magneto-optic disk 1 where the laser beam is applied.
The optical head 31 has an objective lens 3 held in position by a holder 4, and an actuator 33 for keeping the optical axis a of the objective lens 3 perpendicular to the surface of the magneto-optic disk 1 and also for slightly moving the holder 4 and hence the objective lens 3 toward and away from the magneto-optic disk 1 along the optical axis a.
The actuator 33 comprises a coil 36 mounted on the holder 4 and magnetically coupled to a yoke 35 having a magnet 34. When the coil 36 is supplied with a servo signal current, the actuator 33 moves the holder 4 slightly along the optical axis a. The optical head 31 has an optical system including the objective lens 3, the optical system having a laser diode LD for emitting a linearly polarized laser beam. The linearly polarized laser beam emitted from the laser diode LD is converted by a collimator lens CL into a parallel laser beam that is applied through a beam shaper prism BSP and a special beam splitter SBP to a mirror MR1. The laser beam is reflected by the mirror MR1 to pass through the objective lens 3 which focuses the laser beam on the magneto-optic disk 1.
Depending on the information recorded on the magneto-optic disk 1, the laser beam as it is reflected by the magneto-optic disk 1 has its plane of polarization rotated due to the Kerr effect. The laser beam that has returned from the magneto-optic disk 1 is reflected by the mirror MR1 toward the beam splitter SBP. The beam splitter SBP is arranged such that it substantially fully reflects an S-polarized component of the laser beam and it transmits 50% of a P-polarized component of the laser beam and reflects the remaining 50% of the P-polarized component. The S-polarized component, which has been generated by the recorded information on the magneto-optic disk 1, is therefore reflected by the beam splitter SBP toward a polarizer beam splitter PBS.sub.1.
The S-polarized component that is reflected by the polarizer beam splitter PBS.sub.1 is divided into two perpendicular linearly polarized beams by a 1/2.lambda. plate HWP, a condensing lens L.sub.1, and a polarizer beam splitter PBS.sub.2. These two linearly polarized beams are applied respectively to photodetectors PD.sub.1, PD.sub.2 such as photodiodes of an information signal recording/reproducing system, which then differentially produces an information output based on the two linearly polarized beams applied to the photodetectors PD.sub.1, PD.sub.2.
The S-polarized component that is transmitted through the polarizer beam splitter PBS.sub.1 is focused by a lens L.sub.2 onto a central area of a photodetector PD.sub.3 such as a four-segment photodiode, for example. An astigmatic cylindrical lens ASL is placed between the lens L.sub.2 and the photodetector PD.sub.3. If the laser beam applied to the magneto-optic disk 1 is out of focus, then the S-polarized component as it is applied to the photodetector PD.sub.3 is made asymmetric in spot shape by the astigmatic cylindrical lens ASL.
When such a defocused condition is detected by the photodetector PD.sub.3, a servo signal is supplied to the coil 36 of the actuator 33, which then moves the objective lens 3 along the optical axis a in a direction to bring the laser beam into focus on the magneto-optic disk 1. In this manner, the laser beam applied to the magneto-optic disk 1 by the optical head 31 remains focused on the magneto-optic disk 1 at all times.
Consequently, the objective lens 3 is spaced a constant distance from the magneto-optic disk 1 irrespective of disk surface fluctuations, by a servomechanism, which is composed of the actuator 33 and a servo control circuit for controlling the actuator 33. However, such a servomechanism is relatively complex with respect to its mechanical and circuit arrangements.
A magnetic head for recording data on and reproducing data from a magnetic data storage disk such as a magnetic hard disk is usually in the form of a floating magnetic head.
One conventional floating magnetic head is shown in FIGS. 2 and 3 of the accompanying drawings.
As shown in FIGS. 2 and 3, a slider 62 is positioned off the surface of a magnetic data storage disk 1 such as a magnetic hard disk, and a thin-film magnetic head 61 is mounted on the slider 62. As shown in FIG. 2, the slider 62 is mounted on a distal end of a gimbal mechanism 63 and normally resiliently urged toward the magnetic data storage disk 1 under pressure by the gimbal mechanism 63.
As shown FIG. 3, the slider 62 has a rail 64 on its surface facing the magnetic data storage disk 1. When the magnetic data storage disk 1 rotates, an air flow is generated along the rail 64, forcing the slider 62 to be lifted a small distance off the surface of the disk 1 against the resiliency of the gimbal mechanism 63. The surface of the slider 62 which faces the magnetic data storage disk 1, i.e. the rail 64, serves as an air bearing surface. The magnetic head 61 is mounted on the slider 62 such that the magnetic gap of the magnetic head 61 faces the air bearing surface 64.
As shown in FIG. 2, the gimbal mechanism 63 comprises a base plate 65 fixed to a stationary component, a tapered triangular load beam 66 having one end welded to the base plate 65, and a gimbal 67 mounted on the distal end of the load beam 66. The base plate 65, the load beam 66, and the gimbal 67 are made of stainless steel sheet.
As shown in FIG. 3, the gimbal 67 has a resilient tongue 68 which may be cut out of a central area of the gimbal 67. The resilient tongue 68 is bonded to a surface of the slider 62 opposite to the air bearing surface 64 by a resilient adhesive. The resilient tongue 68 has a projection 70 on which the distal end of the load beam 66 is supported in resilient engagement. The slider 62 is coupled to the load beam 66 through the projection 70 on the resilient tongue 68 so that the slider 62 is swingable about the projection 70.
In operation, the slider 62 with the magnetic head 61 is caused to float off the surface of the disk 1 by an air flow that is generated beneath the slider 62 when the magnetic data storage disk 1 rotates. Therefore, the magnetic head 61 remains spaced a certain distance from the surface of the disk 1.
The spacing between the disk 1 and the magnetic head 61 is determined by the air flow produced beneath the slider 62 and the resilient force of the gimbal mechanism 63. It requires a considerable technological level to establish and maintain a desired spacing between the disk 1 and the magnetic head 61. A highly complex process is needed to manufacture and assemble the magnetic disk drive shown in FIGS. 2 and 3. It is therefore difficult to produce magnetic disk drives to desired design specifications.
A floating magnetic head disclosed in Japanese laid-open patent publication No. 52-17811 has an electrostrictive vibrator disposed in a slider. In order to avoid a head crash which might be caused because of a small distance between the magnetic head and a disk surface, the force acting in the gap between the magnetic head and the disk surface and tending to force the magnetic head to float from the disk surface is increased by the electrostrictive vibrator, which is of a laminated structure disposed in the slider, as it transversely vibrates in a direction normal to the disk surface. However, the distance by which the magnetic head floats off the disk surface is essentially determined by an air flow produced upon relative movement of the magnetic head and the disk. Therefore, the problems noted above are not solved by the disclosed floating magnetic head.
Japanese laid-open patent publication No. 57-210479 also discloses a floating magnetic head which includes a piezoelectric body disposed in a slider. When a voltage is applied to the piezoelectric body, the thickness of the slider is increased to adjust a small gap between the magnetic head and a disk surface. Since the distance between the magnetic head and the disk surface is also essentially determined by an air flow produced upon relative movement of the magnetic head and the disk, the disclosed floating magnetic head fails to provide a solution to the aforesaid problems.
A floating magnetic head disclosed in Japanese laid-open patent publication No. 61-178786 comprises a piezoelectric slider. The piezoelectric slider doubles as a shock sensor for detecting a shock applied to the magnetic head. The problems discussed above are not addressed in this publication.
According to Japanese laid-open patent publication No. 63-129515, a floating head has a flexible member and a deforming means which is actuatable by an external signal. The disclosure is directed to the relationship between a slider and a head, and does not show a solution to the above problems since the slider is caused to float off the disk surface by an air flow produced upon relative movement of the disk and the slider.